Low Vision Magnifying Telescopes: Macular Degeneration and Other Vision Loss Conditions

 

 

http://www.LowVisionEyeglasses.com

 

                                    

Telescopic Eyeglasses can greatly improve quality of life, independence and a sense of well-being for adaptable patients with low vision.  Depending on the level of impairment and visual demand, telescopes offer excellent magnification.  They often provide the best option for enhancing available vision when traditional eyeglasses are no longer effective.

Patient expectations must be tempered and realistic goals need to be established.

Telescopes are afocal (parallel light rays entering and leaving the system) consisting of two lenses (objective and ocular) separated in distance by the sum of their focal lengths. 

The patient’s prescription can be incorporated into the carrier lens and/or the telescope.  The telescopes can be mounted in the center position (full diameter), in the superior position (bioptic), or in the inferior position (reading), depending on the visual task required.   

Collimation (optical alignment) and convergence for binocular systems are crucial for best rehabilitation outcomes.  Enhanced illumination is required for reading with tele-microscopes.

Keplerian telescopes have a plus power objective lens and a plus power ocular lens and require an erecting prism or mirror system for the otherwise inverted image.   

 


Keplerian Telescope Diagram

6X Keplerian Telescope
Designs for Vision

1.  Benefits
    A. widest field of view
    B. sharpest edge-to-edge image
    C. superior optical image 4X and stronger

2.  Challengers
    A.  complicated design due to erecting prism/mirrors
    B.  more expensive to fabricate
    C.  smaller exit pupil (more difficult to center and aim)                                   


 

 

Galilean telescopes have a plus power objective lens and a minus power ocular lens. They form an erect and upright image. Galilean telescopes have several functional advantages for low vision rehabilitation especially in lower powers. 

 



Dr. Randolph Kinkade's
Bioptic Rimless Prescription

Galilean Telescope Diagram

 

1.     Benefits

a.      Shorter in length (better cosmetics)

b.      Lighter (no erecting prisms/mirrors)

c.      Large exit pupil (helps with centering)

D.      2 and 3X magnification very functional

2.     Challenges

a.      Narrower field of view and less edge sharpness

b.      Not functional for high power magnification 




Diagnostic Galilean Telescopes



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